U.S. patent application number 14/134545 was filed with the patent office on 2014-06-19 for control system for hydraulic system and method for recovering energy and leveling hydraulic system loads.
The applicant listed for this patent is EATON CORPORATION. Invention is credited to PER WILLIAM DANZL, AARON HERTZEL JAGODA, CHAD ANTHONY LARISH, DAMRONGRIT PIYABONGKARN, MENG (RACHEL) WANG.
Application Number | 20140166114 14/134545 |
Document ID | / |
Family ID | 49943529 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140166114 |
Kind Code |
A1 |
WANG; MENG (RACHEL) ; et
al. |
June 19, 2014 |
CONTROL SYSTEM FOR HYDRAULIC SYSTEM AND METHOD FOR RECOVERING
ENERGY AND LEVELING HYDRAULIC SYSTEM LOADS
Abstract
A control system for a hydraulic system including an accumulator
and a hydraulic transformer coordinates flow sharing within the
hydraulic system. The hydraulic transformer includes first and
second variable displacement pump/motor units mounted on a
rotatable shaft. The rotatable shaft has an end adapted for
connection to a first external load. The first variable
displacement pump/motor unit includes a first side that fluidly
connects to a pump and a second side that fluidly connects to a
tank. The second variable displacement pump/motor unit includes a
first side that fluidly connects to the accumulator and a second
side that fluidly connects with the tank. A second external load
may be hydraulically connected to the hydraulic system. Energy may
be transferred to/from the pump, the accumulator, the first
external load, and/or the second external load, as directed by the
control system.
Inventors: |
WANG; MENG (RACHEL); (EDEN
PRAIRIE, MN) ; JAGODA; AARON HERTZEL; (ST. LOUIS
PARK, MN) ; LARISH; CHAD ANTHONY; (MINNETONKA,
MN) ; PIYABONGKARN; DAMRONGRIT; (MEDINA, MN) ;
DANZL; PER WILLIAM; (EDINA, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EATON CORPORATION |
CLEVELAND |
OH |
US |
|
|
Family ID: |
49943529 |
Appl. No.: |
14/134545 |
Filed: |
December 19, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61739508 |
Dec 19, 2012 |
|
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|
Current U.S.
Class: |
137/12 |
Current CPC
Class: |
E02F 9/2232 20130101;
F15B 2211/214 20130101; F15B 2211/6652 20130101; F15B 2211/88
20130101; E02F 9/2217 20130101; F15B 2211/20569 20130101; F15B
2211/212 20130101; F15B 2211/3059 20130101; F15B 2211/7135
20130101; F15B 21/14 20130101; F15B 2211/6336 20130101; F15B
2211/6306 20130101; F15B 2211/2654 20130101; F15B 2211/6346
20130101; F15B 2211/20546 20130101; F15B 2211/7058 20130101; E02F
9/2075 20130101; Y10T 137/0379 20150401; F15B 2211/633 20130101;
E02F 9/2296 20130101; F15B 2211/761 20130101 |
Class at
Publication: |
137/12 |
International
Class: |
E02F 9/22 20060101
E02F009/22 |
Claims
1. A method of delivering power in a hybrid work machine, the
method comprising: determining engine power of an engine;
determining accumulator pressure of an accumulator; determining a
first target power flow to/from a first work machine component;
determining a second target power flow to/from a second work
machine component; setting an operating mode to a first mode if the
second target power flow is substantially zero; setting the
operating mode to a second mode if the first target power flow is
substantially zero; setting the operating mode to a third mode if
the first and second target power flows are both substantially
non-zero; flow sharing a first power flow from a main pump
mechanically connected to the engine and from a transformer fluidly
connected to the accumulator when the accumulator pressure is below
a first threshold value and the operating mode is set to the first
mode and the accumulator is available for discharge; supplying the
first power flow from the transformer when the accumulator pressure
is above the first threshold value and the operating mode is set to
the first mode; supplying the first power flow from the main pump
when the operating mode is set to the first mode and the
accumulator is unavailable for discharge; flow sharing a second
power flow from the main pump and from the transformer when the
accumulator pressure is below a second threshold value and the
operating mode is set to the second mode and the accumulator is
available for discharge; supplying the second power flow from the
transformer when the accumulator pressure is above the second
threshold value and the operating mode is set to the second mode;
and supplying the second power flow from the main pump when the
operating mode is set to the second mode and the accumulator is
unavailable for discharge.
2. The method of claim 1, further comprising flow sharing the first
power flow from the main pump and from the transformer when the
accumulator pressure is below a third threshold value and the
operating mode is set to the third mode thereby powering the first
work machine component.
3. The method of claim 2, wherein the second work machine component
is powered by the main pump that is mechanically connected to the
engine.
4. The method of claim 1, wherein the hybrid work machine is an
excavator, the first work machine component is a swing actuator,
and the second work machine component is a boom actuator.
5. The method of claim 1, further comprising supplying the first
power flow to the transformer from the first work machine component
and thereby charging the accumulator when the accumulator is
available for charging and the first work machine component is
receiving mechanical power.
6. The method of claim 5, wherein the first power flow is directly
supplied to the transformer by a shaft.
7. The method of claim 1, further comprising supplying the second
power flow to the transformer from the second work machine
component and thereby charging the accumulator when the accumulator
is available for charging and the second work machine component is
receiving mechanical power.
8. The method of claim 7, wherein the second power flow is fluidly
supplied to the transformer by a fluid line.
9. The method of claim 1, further comprising supplying a third
power flow to/from the first work machine component from/to the
second work machine component via the transformer when the
operating mode is set to the third mode.
10. The method of claim 1, further comprising flow sharing a third
power flow to the first work machine component from the second work
machine component and the accumulator when the operating mode is
set to the third mode.
11. The method of claim 1, further comprising flow sharing a third
power flow to the first work machine component from the engine and
the accumulator when the operating mode is set to the third
mode.
12. The method of claim 1, further comprising flow sharing a third
power flow to the second work machine component from the main pump
and the accumulator when the operating mode is set to the third
mode.
13. The method of claim 1, further comprising flow sharing a third
power flow to the accumulator from the second work machine
component and the main pump thereby charging the accumulator when
the accumulator is available for charging and the second work
machine component is receiving mechanical power.
14. A method of delivering power in a hybrid work machine, the
method comprising: determining engine power of an engine;
determining accumulator pressure of an accumulator; determining a
target power flow to/from a work machine component; flow sharing a
power flow to the work machine component from a main pump
mechanically connected to the engine and from a transformer fluidly
connected to the accumulator when the accumulator pressure is below
a threshold value, the accumulator is available for discharge, and
the target power flow is to the work machine component; supplying
the power flow to the work machine component from the transformer
when the accumulator pressure is above the threshold value and the
target power flow is to the work machine component; and supplying
the power flow to the work machine component from the main pump
when the accumulator is unavailable for discharge and the target
power flow is to the work machine component.
15. The method of claim 14, wherein the hybrid work machine is an
excavator and wherein the work machine component is a swing
actuator or a boom actuator.
16. The method of claim 14, wherein the transformer and the work
machine component are mechanically connected by a power transfer
shaft.
17. The method of claim 14, further comprising supplying the power
flow to the transformer from the work machine component and thereby
charging the accumulator when the accumulator is available for
charging and the target power flow is from the work machine
component.
18. The method of claim 17, wherein the power flow is directly
supplied to the transformer from the work machine component by a
power transfer shaft when the accumulator is available for charging
and the target power flow is from the work machine component.
19. The method of claim 17, wherein the power flow is fluidly
supplied to the transformer by a fluid line when the accumulator is
available for charging and the target power flow is from the work
machine component.
20. The method of claim 14, wherein the threshold value is a
variable threshold value.
21. The method of claim 20, wherein the threshold value is
determined prior to determining if the accumulator is available for
discharge.
22. A method of delivering power in a hybrid excavator, the method
comprising: determining engine power of an engine; determining
accumulator pressure of an accumulator; determining a swing target
power flow to/from a swing actuator; determining a boom target
power flow to/from a boom actuator; determining a transformer flow
capacity of a transformer; flow sharing a first power flow from the
boom actuator and from the accumulator to the swing actuator when
the boom actuator is over-running and moving down, the accumulator
is available for discharge, and the boom target power flow is above
a threshold value from the boom actuator; and flow sharing a second
power flow from the swing actuator and from the accumulator to the
boom actuator when the swing actuator is decelerating, the
accumulator is available for discharge, and the swing target power
flow is above a threshold value from the swing actuator.
23. A method of delivering power in a hybrid work machine, the
method comprising: determining accumulator pressure of an
accumulator; determining a target power flow to/from a work machine
component; flow sharing a power flow to the work machine component
from a first power source and from a second power source when the
second power source has available energy below a threshold value,
and the target power flow is to the work machine component;
supplying the power flow to the work machine component from the
second power source when the second power source has the available
energy above the threshold value and the target power flow is to
the work machine component; and supplying the power flow to the
work machine component from the first power source when the second
power source has no available energy and the target power flow is
to the work machine component.
24. The method of claim 23, further comprising determining engine
power of an engine, wherein the first power source is a main pump
mechanically connected to the engine and wherein the second power
source is a transformer fluidly connected to the accumulator at
least when the accumulator has the available energy.
25. The method of claim 23, further comprising determining engine
power of an engine, wherein the work machine component is a first
work machine component, wherein the first power source is a main
pump mechanically connected to the engine, and wherein the second
power source is a transformer fluidly connected to a second work
machine component at least when the second work machine component
has the available energy.
26. The method of claim 23, further comprising determining a target
power flow to/from a second work machine component; wherein the
work machine component is a first work machine component, wherein
the first power source is the second work machine component, and
wherein the second power source is a transformer fluidly connected
to the accumulator at least when the accumulator has the available
energy.
27. A method of delivering power in a hybrid work machine, the
method comprising: determining engine power of an engine;
determining accumulator pressure of an accumulator; determining a
target power flow to/from a work machine component; flow sharing a
power flow to the accumulator from a main pump mechanically
connected to the engine and from a transformer mechanically
connected to the work machine component when the accumulator
pressure is below a threshold value, when the accumulator is
available for charging, and when the target power flow is from the
work machine component; supplying the power flow to the accumulator
from the transformer mechanically connected to the work machine
component when the accumulator pressure is above the threshold
value, when the accumulator is available for charging, and when the
target power flow is from the work machine component; and supplying
the power flow to the accumulator from the transformer fluidly
connected to the main pump when the work machine component has no
available energy.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/739,508, filed Dec. 19,
2012, entitled CONTROL SYSTEM FOR HYDRAULIC SYSTEM AND METHOD FOR
RECOVERING ENERGY AND LEVELING HYDRAULIC SYSTEM LOADS, which
application is hereby incorporated by reference in its
entirety.
BACKGROUND
[0002] Mobile pieces of machinery (e.g., excavators) often include
hydraulic systems having hydraulically powered linear and rotary
actuators used to power various active machine components (e.g.,
linkages, tracks, rotating joints, etc.). Typically, the linear
actuators include hydraulic cylinders and the rotary actuators
include hydraulic motors. By accessing a user interface of a
machine control system, a machine operator can control movement of
the various machine components.
[0003] A typical piece of mobile machinery includes a prime mover
(e.g., a diesel engine, spark ignition engine, electric motor,
etc.) that functions as an overall source of power for the piece of
mobile machinery. Commonly, the prime mover powers one or more
hydraulic pumps that provide pressurized hydraulic fluid for
driving the active machine components of the piece of machinery.
The prime mover is typically required to be sized to satisfy a peak
power requirement of the system. Because the prime mover is
designed to satisfy peak power requirements, the prime mover often
does not operate at peak efficiency under average working
loads.
[0004] The operation of the active hydraulic components of the type
described above can be characterized by frequent accelerations and
decelerations (e.g., overrunning hydraulic loads). Due to
throttling, there is often substantial energy loss associated with
decelerations. There is a need for improved systems for recovering
energy losses associated with such decelerations.
SUMMARY
[0005] One aspect of the present disclosure relates to systems and
methods for effectively recovering and utilizing energy from
overrunning hydraulic loads.
[0006] Another aspect of the present disclosure relates to systems
and methods for leveling the load on a hydraulic systems prime
mover by efficiently storing energy during periods of low loading
and efficiently releasing stored energy during periods of high
loading, thus allowing the prime mover to be sized for average
power requirement rather than for a peak power requirement. Such
systems and methods also permit the prime mover to be run at a more
consistent operating condition which allows an operating efficiency
of the prime mover to be optimized.
[0007] A further aspect of the present disclosure relates to a
hydraulic system including a hydraulic transformer capable of
providing shaft work against an external load. In certain
embodiments, a clutch can be used to engage and disengage the
output shaft from the external load such that the unit can also
function as a stand-alone hydraulic transformer.
[0008] A further aspect of the present disclosure relates to a
control system for the above hydraulic systems and the like.
[0009] A further aspect of the present disclosure relates to
control logic for the above hydraulic systems and the like.
[0010] A variety of additional aspects will be set forth in the
description that follows. These aspects can relate to individual
features and to combinations of features. It is to be understood
that both the foregoing general description and the following
detailed description are exemplary and explanatory only and are not
restrictive of the broad concepts upon which the embodiments
disclosed herein are based.
DRAWINGS
[0011] FIG. 1 is a schematic diagram of a first hydraulic system in
accordance with the principles of the present disclosure;
[0012] FIG. 2 is a matrix table that schematically depicts various
operating modes in which the first hydraulic system of FIG. 1 can
operate;
[0013] FIGS. 3-11 show the first hydraulic system of FIG. 1
operating in the various operating modes outlined in the matrix
table of FIG. 2;
[0014] FIG. 12 is a schematic diagram of a second hydraulic system
in accordance with the principles of the present disclosure;
[0015] FIGS. 13-21 show the second hydraulic system operating in
the various operating modes outlined in the matrix table of FIG.
2;
[0016] FIGS. 22 and 23 are schematic diagrams showing two operating
configurations of a third hydraulic system in accordance with the
principles of the present disclosure;
[0017] FIGS. 24 and 25 show a mobile piece of excavation equipment
that is an example of one type of machine on which hydraulic
systems in accordance with the principles of the present disclosure
can be used;
[0018] FIGS. 26 and 27 are schematic diagrams showing two operating
configurations of a third hydraulic system in accordance with the
principles of the present disclosure;
[0019] FIG. 28 is an enlarged portion of FIG. 27;
[0020] FIG. 29 is a graph of power output of a prime mover of a
conventional example piece of excavation equipment over an example
work cycle;
[0021] FIG. 30 is a graph of power output of a prime mover of an
example piece of excavation equipment over an example work cycle in
accordance with the principles of the present disclosure;
[0022] FIG. 31 is a schematic diagram showing a fourth hydraulic
system, related to the third hydraulic system of FIG. 26, in
accordance with the principles of the present disclosure, the
fourth hydraulic system configured in a mode to raise a boom and
accelerate a swing drive with an operational accumulator and under
high system load of the mobile piece of excavation equipment of
FIGS. 24 and 25;
[0023] FIG. 32 is the schematic diagram of FIG. 31 with the fourth
hydraulic system configured in a mode to raise the boom and
accelerate the swing drive with a transitioning accumulator and
under high system load of the mobile piece of excavation equipment
of FIGS. 24 and 25;
[0024] FIG. 33 is the schematic diagram of FIG. 31 with the fourth
hydraulic system configured in a mode to raise the boom and
accelerate the swing drive with a non-operational accumulator and
under high system load of the mobile piece of excavation equipment
of FIGS. 24 and 25;
[0025] FIGS. 34-39 are example logic flowcharts for operating
example control systems that may be used to control certain
hydraulic systems in accordance with the principles of the present
disclosure;
[0026] FIG. 40 is the schematic diagram of FIG. 31 with the fourth
hydraulic system configured in a mode to raise the boom and
accelerate the swing drive with flow from a main pump raising the
boom and with flow from the main pump and flow from the accumulator
accelerating the swing drive;
[0027] FIG. 41 is the schematic diagram of FIG. 31 with the fourth
hydraulic system configured in a mode to raise the boom and
decelerate the swing drive with flow from the main pump raising the
boom and with the accumulator being charged by the main pump and by
the deceleration of the swing drive;
[0028] FIG. 42 is the schematic diagram of FIG. 31 with the fourth
hydraulic system configured in a mode to lower the boom and
accelerate the swing drive with flow from the main pump lowering
the boom and with the accumulator being charged by the lowering of
the boom and with the acceleration of the swing drive being powered
by the lowering of the boom; and
[0029] FIG. 43 is the schematic diagram of FIG. 31 with the fourth
hydraulic system configured in a mode to raise the boom and charge
the accumulator with flow from the main pump raising the boom and
with the accumulator being charged by the main pump.
DETAILED DESCRIPTION
[0030] Reference will now be made in detail to aspects of the
present disclosure that are illustrated in the accompanying
drawings. Wherever possible, the same reference numbers will be
used throughout the drawings to refer to the same or like
structure.
[0031] FIG. 1 shows a system 10 in accordance with the principles
of the present disclosure. The system 10 includes a variable
displacement pump 12 driven by a prime mover 14 (e.g., a diesel
engine, a spark ignition engine, an electric motor or other power
source). The variable displacement pump 12 includes an inlet 16
that draws low pressure hydraulic fluid from a tank 18 (i.e., a low
pressure reservoir). The variable displacement pump 12 also
includes an outlet 20 through which high pressure hydraulic fluid
is output. The outlet 20 is preferably fluidly coupled to a
plurality of different working load circuits. For example, the
outlet 20 is shown coupled to a first load circuit 22 and a second
load circuit 24. The first load circuit 22 includes a hydraulic
transformer 26 including a first port 28, a second port 30 and a
third port 32. The first port 28 of the hydraulic transformer 26 is
fluidly connected to the outlet 20 of the variable displacement
pump 12 and is also fluidly connected to the second load circuit
24. The second port 30 is fluidly connected to the tank 18. The
third port 32 is fluidly connected to a hydraulic pressure
accumulator 34. The hydraulic transformer 26 further includes an
output/input shaft 36 that couples to an external load 38. A clutch
40 can be used to selectively engage the output/input shaft 36 with
the external load 38 and disengage the output/input shaft 36 from
the external load 38. When the clutch 40 engages the output/input
shaft 36 with the external load 38, torque is transferred between
the output/input shaft 36 and the external load 38. In contrast,
when the clutch 40 disengages the output/input shaft 36 from the
external load 38, no torque is transferred between the output/input
shaft 36 and the external load 38. Gear reductions can be provided
between the clutch 40 and the external load 38.
[0032] The system 10 further includes an electronic controller 42
that interfaces with the prime mover 14, the variable displacement
pump 12, and the hydraulic transformer 26. It will be appreciated
that the electronic controller 42 can also interface with various
other sensors and other data sources provided throughout the system
10. For example, the electronic controller 42 can interface with
pressure sensors incorporated into the system 10 for measuring the
hydraulic pressure in the accumulator 34, the hydraulic pressure
provided by the variable displacement pump 12 to the first and
second load circuits 22, 24, the pressures at the pump and tank
sides of the hydraulic transformer 26 and other pressures.
Moreover, the controller 42 can interface with a rotational speed
sensor that senses a speed of rotation of the output/input shaft
36. Additionally, the electronic controller 42 can be used to
monitor a load on the prime mover 14 and can control the hydraulic
fluid flow rate across the variable displacement pump 12 at a given
rotational speed of a drive shaft 13 powered by the prime mover 14.
In one embodiment, the hydraulic fluid displacement across the
variable displacement pump 12 per shaft rotation can be altered by
changing the position of a swashplate 44 of the variable
displacement pump 12. The controller 42 can also interface with the
clutch 40 for allowing an operator to selectively engage and
disengage the output/input shaft 36 of the transformer 26 with
respect to the external load 38.
[0033] The electronic controller 42 can control operation of the
hydraulic transformer 26 so as to provide a load leveling function
that permits the prime mover 14 to be run at a consistent operating
condition (i.e., a steady operating condition) thereby assisting in
enhancing an overall efficiency of the prime mover 14. The load
leveling function can be provided by efficiently storing energy in
the accumulator 34 during periods of low loading on the prime mover
14, and efficiently releasing the stored energy during periods of
high loading of the prime mover 14. This allows the prime mover 14
to be sized for an average power requirement rather than a peak
power requirement.
[0034] FIG. 2 illustrates a matrix table 50 that schematically
depicts an overview of control logic that can be utilized by the
electronic controller 42 in controlling the operation of the system
10. It will be appreciated that the matrix table 50 is a
simplification and does not take into consideration certain factors
such as the state of charge of the accumulator 34. A primary goal
of the control logic/architecture is to maintain a generally level
loading on the prime mover 14, thus allowing for more efficient
operation of the prime mover 14. The control logic/architecture
also can reduce the system peak power requirement thereby allowing
a smaller prime mover to be used. This is accomplished by using the
accumulator 34 and transformer 26 to recover energy from a first
working circuit powered by the prime mover 14, and to use the
recovered energy as a power supplement for powering a second
working circuit powered by the prime mover 14. The accumulator 34
and the transformer 26 can also be used to buffer the energy
produced by the prime mover 14. The accumulator 34 and the
transformer 26 can further be used to recover energy associated
with load decelerations in a way that can eliminate hydraulic
throttling.
[0035] Referring to FIG. 2, the matrix table 50 includes a
plurality of horizontal rows and a plurality of vertical columns.
For example, the horizontal rows include a first row 52
corresponding to a low loading condition of the prime mover 14, a
second row 54 corresponding to a target loading condition of the
prime mover 14, and a third row 56 corresponding to a high loading
condition of the prime mover 14. The vertical columns include a
first column 58, a second column 60, and a third column 62. The
first column 58 represents a condition where the transformer 26 is
providing a motoring function where torque is being transferred
from the output/input shaft 36 to the external load 38 through the
clutch 40. The second column 60 represents a condition where the
output/input shaft 36 is decoupled from the external load 38 by the
clutch 40. The third column 62 represents a condition where the
transformer 26 is providing a pumping function where torque is
being transferred from the external load 38 back through the
output/input shaft 36.
[0036] Box 64 of the matrix table 50 represents an operating
state/mode where the prime mover 14 is under a low load and the
hydraulic transformer 26 is providing a motoring function in which
torque is being transferred to the external load 38 through the
output/input shaft 36. The system 10 operates in this mode when the
electronic controller 42 receives a command from an operator
interface 43 (e.g., a control panel, joy stick, toggle, switch,
control lever, etc.) instructing the electronic controller 42 to
accelerate or otherwise drive the external load 38 through rotation
of the output/input shaft 36. In this mode/state, the controller 42
controls operation of the hydraulic transformer 26 such that some
hydraulic fluid pressure from the variable displacement pump 12 is
used to drive the output/input shaft 36 and the remainder of the
hydraulic fluid pressure from the variable displacement pump 12 is
used to charge the accumulator 34 (see FIG. 3).
[0037] Box 66 of the matrix table 50 represents an operating
mode/state where the prime mover 14 is operating under a low load
and the output/input shaft 36 is disengaged from the external load
38. In this mode/state, the controller 42 controls operation of the
hydraulic transformer 26 such that the transformer 26 functions as
a stand-alone transformer in which all excess hydraulic fluid
pressure from the variable displacement pump 12 (e.g., excess power
not needed by the second working circuit 24) is used to charge the
accumulator 34 (see FIG. 4). In this way, the transformer 26 and
the accumulator 34 provide an energy buffering function in which
otherwise unused energy from the prime mover 14 is stored for later
use.
[0038] Box 68 of the matrix table 50 represents an operating
mode/state where the prime mover 14 is under a low load and the
transformer 26 is functioning as a pump in which torque is being
transferred into the transformer 26 through the output/input shaft
36. The system 10 operates in this mode/state when the electronic
controller 42 receives a command from the operator interface 43
instructing the electronic controller 42 to decelerate rotation of
the external load 38. This creates an overrunning condition in
which energy corresponding to the movement of the external load 38
(e.g., inertial energy) is converted into torque and transferred
into the transformer 26 through the output/input shaft 36. In this
condition, the electronic controller 42 controls the transformer 26
such that the transformer 26 provides a pumping function that
converts the torque derived from the inertial energy of the
external load 38 into hydraulic energy which is used to charge the
accumulator 34 (see FIG. 5). As energy is transferred to the
accumulator 34, the transformer 26 functions to brake rotation of
the output/input shaft 36 to achieve the desired deceleration. In
this mode/state, the electronic controller 42 can also control the
transformer 26 such that excess energy from the variable
displacement pump 12 is concurrently used to charge the accumulator
34.
[0039] Box 70 of the matrix table 50 represents a mode/state where
the prime mover 14 is operating at a target load and the hydraulic
transformer 26 is providing a motoring function in which the
output/input shaft 36 drives the external load 38. In this
mode/state, the electronic controller 42 controls the transformer
26 such that energy from the variable displacement pump 12 is used
to drive the output/input shaft 36 and no energy is transferred to
the accumulator 34 (see FIG. 6).
[0040] Box 72 represents a mode/state where the prime mover 14 is
at a target load and the output/input shaft 36 is disengaged from
the external load 38. In this mode/state, the electronic controller
42 controls the transformer 26 such that no energy is transferred
through the hydraulic transformer 26 (see FIG. 7).
[0041] Box 74 of the matrix table 50 is representative of a
mode/state where the prime mover 14 is at a target load and the
transformer 26 is functioning as a pump in which torque is being
transferred into the transformer 26 through the output/input shaft
36. The system 10 operates in this mode/state when the electronic
controller 42 receives a command from the operator interface 43
instructing the electronic controller 42 to decelerate rotation of
the external load 38. This creates an overrunning condition in
which energy corresponding to the movement of the external load 38
(e.g., inertial energy) is converted into torque and transferred
into the transformer 26 through the output/input shaft 36. In this
mode/state, the electronic controller 42 controls the transformer
26 such that the transformer 26 provides a pumping function that
converts the torque derived from the inertial energy of the
external load 38 into hydraulic energy which is used to charge the
accumulator 34 (see FIG. 8). As energy is transferred to the
accumulator 34, the transformer 26 functions to brake rotation of
the output/input shaft 36 to achieve the desired deceleration.
[0042] Box 76 of the matrix table 50 is representative of an
operating mode/state where the prime mover 14 is operating under a
high load and the transformer 26 provides motoring function in
which the output/input shaft 36 drives the external load 38. In
this mode/state, the controller 42 controls the transformer 26 such
that energy from the accumulator 34 is used to rotate the
output/input shaft 36 for driving the external load 38. Also, the
transformer 26 is controlled by the controller 42 such that excess
energy from the accumulator 34 can be concurrently transferred back
toward the variable displacement pump 12 and the second load
circuit 24 (see FIG. 9) to assist in leveling/reducing the load on
the prime mover 14.
[0043] Box 78 of the matrix table 50 is representative of an
operating mode/state where the prime mover 14 is operating under a
high load condition and the output/input shaft 36 is disconnected
from the external load 38. In this condition, the electronic
controller 42 controls the transformer 26 such that energy from the
accumulator 34 is directed through the hydraulic transformer 26
back toward the pump 12 and the second load circuit 24 for use at
the second load circuit 24 (see FIG. 10) to assist in
leveling/reducing the load on the prime mover 14. It will be
appreciated that the pump 12 and the second load circuit 24 can be
referred to as the "system side" of the overall hydraulic system
10.
[0044] Box 80 of the matrix table 50 is representative of an
operating mode/state where the prime mover 14 operating under a
high load and the transformer 26 is functioning as a pump in which
torque is being transferred into the transformer 26 through the
output/input shaft 36. The system 10 operates in this mode/state
when the electronic controller 42 receives a command from the
operator interface 43 instructing the electronic controller 42 to
decelerate rotation of the external load 38. This creates an
overrunning condition in which energy corresponding to the movement
of the external load 38 (e.g., inertial energy) is converted into
torque and transferred into the transformer 26 through the
output/input shaft 36. In this mode/state, the electronic
controller 42 controls the transformer 26 such that the transformer
26 provides a pumping function that converts the torque derived
from the inertial energy of the external load 38 into hydraulic
energy which is directed toward the system side of the hydraulic
system 10 and used to assist in leveling/reducing the load on the
prime mover 14. As energy is transferred to the system side, the
transformer 26 functions to brake rotation of the output/input
shaft 36 to achieve the desired deceleration. In this condition,
the electronic controller 42 can also control the transformer 26
such that energy from the accumulator 34 is concurrently directed
back toward the system side of the overall hydraulic system 10 and
the second load circuit 24 for use at the second load circuit 24
(see FIG. 11).
[0045] FIG. 12 shows the system 10 of FIGS. 1-11 equipped with a
hydraulic transformer 26a having a plurality of pump/motor units
connected by a common shaft. For example, the hydraulic transformer
26a includes first and second variable volume positive displacement
pump/motor units 100, 102 connected by a shaft 104. The shaft 104
includes a first portion 106 that connects the first pump/motor
unit 100 to the second pump/motor unit 102, and a second portion
108 that forms the output/input shaft 36. The first pump/motor unit
100 includes a first side 100a fluidly connected to the variable
displacement pump 12 and a second side 100b fluidly connected to
the tank 18. The second pump/motor unit 102 includes a first side
102a fluidly connected to the accumulator 34 and a second side 102b
fluidly connected to the tank 18.
[0046] In one embodiment, each of the first and second pump/motor
units 100, 102 includes a rotating group (e.g., cylinder block and
pistons) that rotates with the shaft 104, and a swash plate 110
that can be positioned at different angles relative to the shaft
104 to change the amount of pump displacement per each shaft
rotation. The volume of hydraulic fluid displaced across a given
one of the pump/motor units 100, 102 per rotation of the shaft 104
can be varied by varying the angle of the swash plate 110
corresponding to the given pump/motor unit. Varying the angle of
the swash plate 110 also changes the torque transferred between the
shaft 104 and the rotating group of a given pump/motor unit. When
the swash plates 110 are aligned perpendicular to the shaft 104, no
hydraulic fluid flow is directed through the pump/motor units 100,
102. The swash plates 110 can be over-the-center swash plates that
allow for bi-directional rotation of the shaft 104. The angular
positions of the swash plates 110 are individually controlled by
the electronic controller 42 based on the operating condition of
the system 10.
[0047] By controlling the positions of the swash plates 110, the
controller 42 can operate the system 10 in any one of the operating
modes set forth in the matrix table 50 of FIG. 2. When the system
10 is operated in the mode of box 64, the first pump/motor unit 100
uses power from the pump 12 to turn the shaft 104 and drive the
external load 38, and the second pump/motor unit 102 takes power
off the shaft 104 and uses the power to pump hydraulic fluid into
the accumulator 34 (see FIG. 13). When the system 10 is operated in
the mode of box 66, the first pump/motor unit 100 uses power from
the pump 12 to turn the shaft 104, and the second pump/motor unit
102 takes power off the shaft 104 and uses the power to pump
hydraulic fluid into the accumulator 34 to charge the accumulator
34 (see FIG. 14). When the system 10 is operated in the mode of box
68, inertial energy from the moving external load 38 turns the
shaft 104, and the second pump/motor unit 102 takes power off the
shaft 104 and uses the power to pump hydraulic fluid into the
accumulator 34 to charge the accumulator 34 (see FIG. 15). Energy
from the pump 12 can also be concurrently used to charge the
accumulator 34. When the system 10 is operated in the mode of box
70, the first pump/motor unit 100 uses power from the pump 12 to
turn the shaft 104 and drive the external load 38, and the second
pump/motor unit 102 is set to zero displacement (see FIG. 16). When
the system 10 is operated in the mode of box 72, both of the
pump/motor units 100, 102 are set to zero displacement (see FIG.
17). When the system 10 is operated in the mode of box 74, inertial
energy from the moving external load 38 turns the shaft 104, and
the second pump/motor unit 102 takes power off the shaft 104 and
uses the power to pump hydraulic fluid into the accumulator 34 to
charge the accumulator 34, and the first pump/motor 100 is set to
zero displacement (see FIG. 18). When the system 10 is operated in
the mode of box 76, the second pump/motor unit 102 uses power from
the charged accumulator 34 to turn the shaft 104 and drive the
external load 38, and the first pump/motor unit 101 pumps hydraulic
fluid back toward the pump 12 and the second load circuit 24 (see
FIG. 19). When the system 10 is operated in the mode of box 78, the
second pump/motor unit 102 uses power from the charged accumulator
34 to turn the shaft 104, and the first pump/motor unit 101 pumps
hydraulic fluid back toward the pump 12 and the second load circuit
24 (see FIG. 20). When the system 10 is operated in the mode of box
80, the second pump/motor unit 102 uses power from the charged
accumulator 34 to turn the shaft 104, inertial energy from the
moving external load 38 also turns the shaft 104, and the first
pump/motor unit 101 pumps hydraulic fluid back toward the pump 12
and the second load circuit 24 (see FIG. 21).
[0048] By controlling the displacement rates and displacement
directions of the pump/motor units 100, 102, fluid power (pressure
times flow) at a particular level can be converted to an alternate
level, or supplied as shaft power used to drive the external load
38. When a deceleration of the external load 38 is desired, the
hydraulic transformer 26a can act as a pump taking low pressure
fluid from the tank 18 and directing it either to the accumulator
34 for storage, to the second load circuit 24 connected to the
variable displacement pump 12, or a combination of the two. By
using the clutch 40 to disengage the output/input shaft 36 from the
external load 38, the hydraulic transformer 26a can function as a
stand-alone hydraulic transformer (e.g., a conventional hydraulic
transformer) when no shaft work is required to be applied to the
external load 38. This is achieved by taking energy from the system
10 at whatever pressure is dictated by the other associated system
loads (e.g., the load corresponding to the second load circuit 24)
and storing the energy, without throttling, at the current
accumulator pressure. In the same way, unthrottled energy can also
be taken from the accumulator 34 at its current pressure and
supplied to the system 10 at the desired operating pressure.
Proportioning of power flow by the hydraulic transformer 26a can be
controlled by controlling the positions of the swash plates 110 on
the pump/motor units 100, 102. In certain embodiments, aspects of
the present disclosure can be used in systems without a clutch for
disengaging a connection between the output/input shaft 36 and the
external load 38.
[0049] FIG. 22 shows another system 210 in accordance with the
principles of the present disclosure. This system 210 includes a
variable displacement pump 212 powered by a prime mover 214. The
variable displacement pump 212 draws hydraulic fluid from a tank
218 and outputs pressurized hydraulic fluid for powering a first
load circuit 222, a second load circuit 224, and a third load
circuit 226. A control valve arrangement 227 controls fluid
communication between the variable displacement pump 212 and the
second and third load circuits 224, 226. The first load circuit 222
includes a hydraulic transformer 26b including three rotating
groups connected by a common shaft 229. The common shaft 229
includes an end portion forming an output/input shaft 236. A clutch
240 is used to selectively couple the output/input shaft 236 to an
external load 238 and to selectively decouple the output/input
shaft 236 from the external load 238.
[0050] The rotating groups of the hydraulic transformer 26b include
a first variable displacement pump/motor unit 200, a second
variable displacement pump/motor unit 202, and a third variable
displacement pump/motor unit 203. A first side 270 of the first
pump/motor unit 200 is fluidly connected to an output side of the
variable displacement pump 212 and a second side 271 of the first
pump/motor unit 200 is fluidly connected to the tank 218. A first
side 272 of the third pump/motor unit 203 is fluidly connected to a
flow line 281 that connects to the second load circuit 224. A flow
control valve 280 is positioned along the flow line 281. A second
side 273 of the third pump/motor unit 203 is fluidly connected to
the tank 218. A first side 274 of the second pump/motor unit 202 is
fluidly connected to a hydraulic pressure accumulator 234, and a
second side 275 of the third pump/motor unit 203 is fluidly
connected to the tank 218. The pump/motors 200, 202, and 203 can
have the same type of configuration as the pump/motors previously
described herein.
[0051] The second load circuit 224 includes a hydraulic cylinder
295 having a piston 296 mounted within a cylinder body 297. The
piston 296 is movable in a lift stroke direction 298 and a return
stroke direction 299. When the piston 296 is moved in the lift
stroke direction 298, the hydraulic cylinder 295 is used to lift or
move a work element 301 (e.g., a boom) against a force of gravity.
The work element 301 moves with the force of gravity when the
piston 296 moves in the return stroke direction 299. The cylinder
body 297 defines first and second ports 302, 303 positioned on
opposite sides of a piston head 304 of the piston 296.
[0052] To drive the piston 296 in the lift stroke direction 298,
hydraulic fluid is pumped from the pump 212 through the control
valve arrangement 227 and the flow control valve 280 into the
cylinder body 297 through the first port 302. Concurrently,
movement of the piston head 304 in the lift stroke direction 298
forces hydraulic fluid out of the cylinder body 297 through the
second port 303. The hydraulic fluid exiting the cylinder body 297
through the second port 303 flows through the control valve
arrangement 227 which directs the hydraulic fluid to the tank
218.
[0053] To move the piston 296 in the return stroke direction 299,
hydraulic fluid is pumped from the pump 212 through the control
valve arrangement 227 into the cylinder body 297 through the second
port 303. Concurrently, movement of the piston head 304 in the
return stroke direction 299 forces hydraulic fluid out of the
cylinder body 297 through the first port 302. Movement of the
piston head 304 in the return stroke direction 299 is gravity
assisted/powered (e.g., by the weight of the lifted work element
301) causing the hydraulic fluid exiting the first port 302 to be
pressurized. By shifting the flow control valve 280 as shown at
FIG. 23, the hydraulic fluid output from the first port 302 during
the return stroke of the piston 296 can be routed through the flow
line 281 to the third pump/motor unit 203 such that energy from the
pressurized fluid exiting the cylinder body 297 can be used to
drive the common shaft 229. As the common shaft 229 is driven by
pressure released from the hydraulic cylinder 295, energy
corresponding to the return stroke of the piston 296 can be
transferred to the accumulator 234 through the second pump/motor
unit 202 and/or can be transferred to the external load 238 through
the output/input shaft 236. Additionally, the energy can also be
transferred back toward the variable displacement pump 212 in the
form of pressurized hydraulic fluid pumped out the first side 270
of the first pump/motor unit 200. In this way, the hydraulic
transformer 26b allows for the recovery and use of potential energy
corresponding to the lifted weight of the work element 301 which
was elevated during the lift stroke of the hydraulic cylinder
295.
[0054] Similar to the previously described embodiments, the
transformer 26b and accumulator 234 also allow excess energy from
the pump 212 to be stored in the accumulator 234 to provide an
energy buffering function. Also, similar to the previously
described embodiments, energy corresponding to a deceleration of
the working load 238 can be stored in the accumulator 234 for later
use and/or directed back toward the pump 212 for use at the second
or third load circuits 224, 226 to provide a load leveling
function. Additionally, the valve 280 and third pump/motor unit 203
also allow energy from the accumulator 34 or corresponding to a
deceleration of the working load 238 to be used to drive the piston
296 in the lift direction 298. As compared to the modes set forth
at FIG. 2, the addition of the third pump/motor unit 203 linked to
another circuit that can both draw power and supply power provides
additional sets of operating modes/options.
[0055] In one example embodiment, hydraulic circuit configurations
of the type described above can be incorporated into a piece of
mobile excavation equipment such as an excavator. For example,
FIGS. 24 and 25 depict an example excavator 400 including an upper
structure 412 supported on an undercarriage 410. The undercarriage
410 includes a propulsion structure for carrying the excavator 400
across the ground. For example, the undercarriage 410 can include
left and right tracks. The upper structure 412 is pivotally movable
relative to the undercarriage 410 about a pivot axis 408 (i.e., a
swing axis). In certain embodiments, transformer input/output
shafts of the type described above can be used for pivoting the
upper structure 412 about the swing axis 408 relative to the
undercarriage 410.
[0056] The upper structure 412 can support and carry the prime
mover 14 of the machine and can also include a cab 425 in which an
operator interface is provided. A boom 402 is carried by the upper
structure 412 and is pivotally moved between raised and lowered
positions by a boom cylinder 402c. An arm 404 is pivotally
connected to a distal end of the boom 402. An arm cylinder 404c is
used to pivot the arm 404 relative to the boom 402. The excavator
400 also includes a bucket 406 pivotally connected to a distal end
of the arm 404. A bucket cylinder 406c is used to pivot the bucket
406 relative to the arm 404. In certain embodiments, the boom
cylinder 402c, the arm cylinder 404c, and the bucket cylinder 406c
can be part of system load circuits of the type described above.
For example, the hydraulic cylinder 295 of the embodiment of FIGS.
22 and 23 can function as the boom cylinder 402c.
[0057] FIGS. 26-28 illustrate another system 510 in accordance with
the principles of the present disclosure that is adapted for use
with the excavator 400. This system 510 includes a variable
displacement pump 512 powered by a prime mover 514. The variable
displacement pump 512 can include a swash plate 544 for controlling
the pump displacement volume per shaft rotation. A system
controller 542 can interface with a negative flow control circuit
543 having a negative flow control orifice valve 545 (e.g., a
proportional flow control valve). The negative flow control circuit
543 allows a negative flow control (NFC) pump control strategy to
be used to control operation of the pump 512. The variable
displacement pump 512 draws hydraulic fluid from a tank 518 and
outputs pressurized hydraulic fluid for powering a first load
circuit 522, a second load circuit 524, and a third load circuit
526. The second load circuit 524 includes the arm cylinder 404c and
the third load circuit 526 includes the boom cylinder 402c. A
direction flow control valve 523 (e.g., a proportional direction
flow control valve) controls fluid flow between the arm cylinder
404c and the pump 512 and the tank 518. A direction flow control
valve 525 (e.g., a proportional direction flow control valve)
controls fluid flow between the boom cylinder 402c and the pump 512
and the tank 518. The first load circuit 522 includes a hydraulic
transformer 26c including two rotating groups connected by a common
shaft 529. The common shaft or shafts 529 include an end portion
forming an output/input shaft 536. A clutch 540 is used to
selectively couple the output/input shaft 536 to an external load
538 and to selectively decouple the output/input shaft 536 from the
external load 538. The output/input shaft 536 is preferably used to
pivot (i.e., swing) the upper structure 412 of the excavator 400
about the pivot axis 408 relative to the undercarriage 410. Thus,
the external load 538 represents the load used to accelerate and
decelerate pivotal movement of the upper structure 412 about the
pivot axis 408. A gear reduction 539 is shown between the clutch
540 and the upper structure 412.
[0058] The rotating groups of the hydraulic transformer 26c include
a first variable displacement pump/motor unit 500 and a second
variable displacement pump/motor unit 502. A first side 570 of the
first pump/motor unit 500 is fluidly connected to an output side of
the variable displacement pump 512 and a second side 571 of the
first pump/motor unit 500 is fluidly connected to the tank 518. A
flow line 569 connects the second side 571 of the first pump/motor
unit 500 to the output side of the pump 512. A first side 574 of
the second pump/motor unit 502 is fluidly connected to a hydraulic
pressure accumulator 534, and a second side 575 of the second
pump/motor unit 502 is fluidly connected to the tank 518. The
pump/motors 500, 502 can have the same type of configuration as the
pump/motors previously described herein.
[0059] The boom cylinder 402c includes a cylinder 405 and a piston
407. The cylinder 405 defines first and second ports 409, 411 on
opposite sides of a piston head 413 of the piston 407.
[0060] A flow control valve 567 (i.e., a mode valve) is positioned
along the flow line 569. In certain embodiments, the flow control
valve 567 is a proportional flow control valve. The flow control
valve 567 is movable between first and second positions. In the
first position, the flow control valve 567 fluidly connects the
output side of the pump 512 to the first side 570 of the first
pump/motor unit 500. In the second position (shown at FIG. 27), the
flow control valve 567 fluidly connects the first port 409 of the
cylinder 405 to the first side 570 of the first pump/motor unit
500. To move the piston 407 in a lift/extension stroke to lift the
boom 402, the first port 409 may be placed in fluid communication
with the output side of the pump 512 and the second port 411 may be
placed in fluid communication with the tank 518, and/or the first
port 409 may be placed in fluid communication with the first side
570 of the first pump/motor unit 500 and the second port 411 may be
placed in fluid communication with the tank 518. To move the piston
407 in a return direction to lower the boom 402, the first port 409
may be placed in fluid communication with the first side 570 of the
first pump/motor unit 500 through the flow control valve 567. In
certain embodiments, a one-way check valve 563 prevents the first
port 409 from being placed in fluid communication with the tank 518
as the boom 402 is lowered in this configuration. It will be
appreciated that the weight of the boom 402 pressurizes the
hydraulic fluid exiting the first port 409 as the boom 402 is
lowered. By directing such pressurized hydraulic fluid to the
transformer 26c, potential energy corresponding to the weight of
the elevated boom 402 can be recovered and stored in the
accumulator 534 and/or can be transferred to the external load 538
through the output/input shaft 536. Additionally, in certain
embodiments, the energy can also be transferred back toward the
variable displacement pump 512 in the form of pressurized hydraulic
fluid pumped out of the first side 570 of the first pump/motor unit
500. In this way, the hydraulic transformer 26c allows for the
recovery and use of potential energy corresponding to the lifted
weight of the boom 402 which was elevated during the lift stroke of
the hydraulic cylinder 402c.
[0061] Similar to the previously described embodiments, the
transformer 26c and accumulator 534 also allow excess energy from
the pump 512 to be stored in the accumulator 534 to provide an
energy buffering function. Also, similar to the previously
described embodiments, energy corresponding to a deceleration of
the working load 538 can be stored in the accumulator 534 for later
use, directed to the boom cylinder 402c, and/or directed back
toward the pump 512 for use at the second or third load circuits
524, 526 to provide a load leveling function. Hydraulic fluid
pressure sensors 590 interfacing with the controller 542 are
provided throughout the system 510.
[0062] FIG. 29 illustrates (i.e., graphs) a power output of a prime
mover (e.g., a diesel engine) of a conventional work machine (e.g.,
an excavator) over a typical work cycle (e.g., a digging cycle). A
power peak may occur when high demand is required and/or requested
to perform a portion of the typical work cycle. Such power peaks
are especially likely to occur when the high demand is required
and/or requested of several services simultaneously (e.g., boom
raising and upper structure swinging). Conversely, a power trough
(i.e., power underutilization) may occur when low demand is
required during another portion of the typical work cycle. The
prime mover and/or one or more hydraulic supply pumps of the
conventional work machine may be sized to accommodate the power
peaks. Over the work cycle, an average engine power can be
determined by dividing engine energy produced by cycle time. The
average engine power may be substantially less than the peak power.
Efficiency of the prime mover may be reduced when operating at low
load levels and/or when transitioning between significant
differences in load levels. The systems of the present disclosure
may substantially improve efficiency of the prime mover by leveling
the power output of the prime mover.
[0063] FIG. 30 illustrates (i.e., graphs) a power output of a prime
mover (e.g., a diesel engine) of a work machine (e.g., an
excavator), similar to the conventional work machine of FIG. 29,
over a typical work cycle (e.g., a digging cycle), similar to the
typical work cycle of FIG. 29. In contrast, the work machine of
FIG. 30 includes a hydraulic system in accordance with the
principles of the present disclosure such as the hydraulic system
10, 210, 510. The hydraulic system 10, 210, 510 lowers the required
engine power output over the typical work cycle by load leveling
and energy recycling. This provides benefits including allowing a
smaller prime mover to be used in the work machine (i.e., reducing
engine size), increased efficiency from energy recycling (i.e.,
energy regeneration), increased efficiency from more closely
matching engine peak efficiency over longer durations of the
typical work cycle (i.e., engine efficiency optimization),
increased efficiency from a lower weight of a smaller engine (e.g.,
lower swing inertia), lower cost for the smaller engine, longer
engine life from running the engine at steadier output loads,
etc.
[0064] In accordance with the principles of the present disclosure,
a control system, such as the system controller 542, is adapted for
controlling the hydraulic system, such as the hydraulic system 510.
Described hereinafter are example methods of operation of the
control system. A primary goal of the control logic/architecture is
to maintain a generally level loading on the prime mover (e.g., the
prime mover 514), thus allowing for more efficient operation of the
prime mover. The control logic/architecture also can reduce the
system peak power requirement thereby allowing a smaller prime
mover to be used.
[0065] A goal of the hydraulic system 510 is to emulate a
conventional hydraulic system and thereby have operating
characteristics that are the same as or similar to the conventional
hydraulic system. In particular, the operator of the work machine
(e.g., the excavator 400) may operate the work machine with the
hydraulic system 510 in the same way or in a similar way as the
work machine with a conventional hydraulic system. The system
controller 542 receives commands generated by an operator interface
manipulated by the operator. The system controller 542 monitors the
hydraulic system 510 and interprets the commands with consideration
of various states and conditions of the excavator 400. These
include the state of the boom 402, the state of the swing of the
upper structure 412, the state of the accumulator 534, and the
state of engine load. By processing these various inputs, the
system controller 542 generates appropriate control signals to
effect the input of the operator.
[0066] In preferred embodiments, the hydraulic system 510 includes
multiple actuators and may include both linear and rotary
actuators. The hydraulic system 510 may include energy recovery and
reuse from the actuators and may level the load of the actuators on
the engine. The hydraulic system 510 does not require independent
meter-in and meter-out control of the actuators. The hydraulic
system 510 may exchange energy among multiple components including
the swing of the upper structure 412, movement of the boom 402, the
primary pump 512, and the accumulator 534. Energy recovery and
engine load leveling may occur with respect to multiple actuators
simultaneously.
[0067] Turning now to FIGS. 31-33 and 40-43, the system 510 further
includes valves 415 and 417 and discards, bypasses, and/or disables
the one-way check valve 563 in comparison with the system 510 as
illustrated at FIGS. 26-28. The valve 415 is connected between the
ports 409 and 411 of the cylinder 402c. The valve 417 is connected
between the port 411 of the cylinder 402c and the tank 518. The
valves 415, 417 as illustrated, are proportional valves. The valves
415, 417 may provide the cylinder 402c with alternative flow paths
depending on the positioning of the valves 523, 525, 567.
[0068] In FIGS. 31-33, the system 510 is illustrated in a Mode 1
(i.e., M1). In particular, FIG. 31 illustrates a Sub-mode M1a, FIG.
32 illustrates a Sub-mode M1t, and FIG. 33 illustrates a Sub-mode
M1b. Mode 1 includes the boom 402 being raised and the upper
structure 412 being rotationally accelerated while the system load
is high.
[0069] The accumulator 534 in the Sub-mode M1a is sufficiently
charged to supply energy to the system 510 (e.g., an actual
accumulator pressure, Pacc, >a low set-point accumulator
pressure, Plow). As indicated at FIG. 31, the Sub-mode M1a
configures the pump/motor 502 as a motor, configures the pump/motor
500 as a pump, sets the mode valve 567 to fluidly connect with the
boom cylinder 402c, opens the NFC valve 545, engages the clutch
540, disengages the brake 533, and positions the direction flow
control valve 525 to neutral. The system 510 may remain in the
Sub-mode M1a until the operator inputs a command that no longer
raises the boom 402 or rotationally accelerates the upper structure
412, the system load is reduced from "high", and/or the accumulator
534 sufficiently discharges such that it can no longer meet the
power demanded by the boom 402 and the upper structure 412
simultaneously.
[0070] Upon the accumulator 534 sufficiently discharging such that
it no longer can meet the power demanded by the boom 402 and the
upper structure 412, the system controller 542 automatically
configures the system 510 to the Sub-mode M1t. As indicated at FIG.
32, the Sub-mode M1t configures the pump/motor 502 as a motor
initially, configures the pump/motor 500 as a pump initially, sets
the mode valve 567 to fluidly connect with the boom cylinder 402c
initially, opens the NFC valve 545 initially, engages the clutch
540, and positions the direction flow control valve 525 to neutral
initially. The system 510 may remain in the Sub-mode M1t until the
operator inputs a command that no longer raises the boom 402 or
rotationally accelerates the upper structure 412, the system load
is reduced from "high", and/or the accumulator 534 sufficiently
discharges such that it can no longer provide power to the boom 402
and the upper structure 412. The Sub-mode M1t smoothly transitions
the system 510 from the Sub-mode M1a to the Sub-mode M1b and thus
changes (e.g., continuously changes) a displacement of the
pump/motor 502, a displacement of the pump/motor 500, the mode
valve 567, the NFC valve 545, and the direction flow control valve
525. The displacement of the pump/motor 502 may initially increase
to generate torque while the accumulator 534 is depleted, and, when
the accumulator 534 is depleted, the displacement of the pump/motor
502 is set to 0. The displacement of the pump/motor 500 may
continuously be adjusted to supply the required torque and speed to
the output/input shaft 536 while the accumulator 534 is depleted
and the mode valve 567 and the NFC valve 545 are reconfigured. The
mode valve 567 is reconfigured from supplying hydraulic power to
the boom 402 to receiving hydraulic power from the primary pump 512
in conjunction with the pump/motor 500 switching from a pump to a
motor. The NFC valve 545 transitions from open to restricted to set
the appropriate displacement of the primary pump 512. The direction
flow control valve 525 changes from neutral to a position
appropriate for the operation of the boom cylinder 402c.
[0071] Upon the accumulator 534 discharging such that it no longer
can supply power to the boom 402 and the upper structure 412, the
system controller 542 automatically configures the system 510 to
the Sub-mode M1b. As indicated at FIG. 33, the Sub-mode M1b keeps
the pump/motor 502 configured at 0 displacement, keeps the
pump/motor 500 configured as a motor, keeps the mode valve 567
fluidly connected with the engine (i.e., the primary pump 512),
keeps the NFC valve 545 restricted, keeps the clutch 540 engaged,
and positions the direction flow control valve 525 to a position
appropriate for the operation of the boom cylinder 402c. The system
510 may remain in the Sub-mode M1b until the operator inputs a
command that no longer raises the boom 402 or rotationally
accelerates the upper structure 412 or the system load is reduced
from "high".
[0072] The system 510 is illustrated in a Mode 2 (i.e., M2) at FIG.
42. The Mode 2 includes the boom 402 being lowered-overrunning and
the upper structure 412 being rotationally accelerated while the
system load is on target. The accumulator 534 in a Sub-mode 2a is
sufficiently depleted to receive energy from the system 510 (e.g.,
the actual accumulator pressure, Pacc, <a high set-point
accumulator pressure, Phigh). The Sub-mode 2a configures the
pump/motor 502 as a pump, configures the pump/motor 500 as a motor,
sets the mode valve 567 to fluidly connect with the boom cylinder
402c, opens the NFC valve 545, engages the clutch 540, and
positions the direction flow control valve 525 to neutral. The
system 510 may remain in the Sub-mode 2a until the operator inputs
a command that no longer lowers the boom 402 or rotationally
accelerates the upper structure 412, the system load is no longer
"on-target", and/or the accumulator 534 sufficiently charges such
that it can no longer receive power.
[0073] Upon the accumulator 534 approaching sufficient charge, such
that it can no longer receive power, the system controller 542
automatically configures the system 510 to a Sub-mode 2t. The
Sub-mode 2t configures the pump/motor 502 as a pump initially. The
pump/motor 500 remains a motor. The mode valve 567 remains fluidly
connected with the boom cylinder 402c. The NFC valve 545 remains
open. The clutch 540 remains engaged. And, the direction flow
control valve 525 remains at neutral. The system 510 may remain in
the Sub-mode 2t until the operator inputs a command that no longer
lowers the boom 402 or rotationally accelerates the upper structure
412, the system load is changed from "on-target", and/or the
accumulator 534 sufficiently charges such that it can no longer
receive power. The Sub-mode 2t smoothly transitions the system 510
from the Sub-mode 2a to the Sub-mode 2b and thus changes (e.g.,
continuously changes) the displacement of the pump/motor 502. The
displacement of the pump/motor 502 may be set to match the
accumulator 534, and, when the accumulator 534 is fully charged,
the displacement of the pump/motor 502 is set to 0. The
displacement of the pump/motor 500 may continuously be adjusted to
supply the required torque and speed to the output/input shaft 536
while the accumulator 534 is charging.
[0074] Upon the accumulator 534 charging such that it no longer can
receive power, the system controller 542 automatically configures
the system 510 to a Sub-mode 2b. The Sub-mode 2b keeps the
pump/motor 502 configured at 0 displacement, keeps the pump/motor
500 configured as a motor, keeps the mode valve 567 set to fluidly
connected with the boom cylinder 402c, keeps the NFC valve 545
open, keeps the clutch 540 engaged, and keeps the direction flow
control valve 525 positioned at neutral. The system 510 may remain
in the Sub-mode 2b until the operator inputs a command that no
longer lowers the boom 402 or rotationally accelerates the upper
structure 412 or the system load changes from "on-target".
[0075] The system 510 may further be configured in a Mode 3 (i.e.,
M3). The Mode 3 includes the boom 402 being lowered-overrunning and
the upper structure 412 being rotationally decelerated while the
system load is on target. The accumulator 534 in a Sub-mode 3a is
sufficiently depleted (i.e., discharged, below maximum capacity,
etc.) to receive energy from the system 510. In particular, the
accumulator 534 in the Sub-mode 3a is sufficiently depleted (i.e.,
Pacc<Phigh) to receive energy from the hydraulic cylinder 402c
via the transformer 26c and/or the transformer 26c which receives
shaft power from the swing drive directly via the output/input
shaft 536. The Sub-mode 3a configures the pump/motor 502 as a pump,
configures the pump/motor 500 as a motor, sets the mode valve 567
to fluidly connect with the boom cylinder 402c, opens the NFC valve
545, engages the clutch 540, and positions the direction flow
control valve 525 to neutral. The system 510 may remain in the
Sub-mode 3a until the operator inputs a command that no longer
lowers the boom 402 or rotationally decelerates the upper structure
412, the system load is no longer "on-target", and/or the
accumulator 534 sufficiently charges such that it can no longer
receive power.
[0076] Upon the accumulator 534 approaching sufficient charge, such
that it can no longer receive power, the system controller 542
automatically configures the system 510 to a Sub-mode 3t. The
Sub-mode 3t configures the pump/motor 502 as a pump initially. The
pump/motor 500 remains a motor. The mode valve 567 remains fluidly
connected with the boom cylinder 402c. The NFC valve 545 remains
open. The clutch 540 remains engaged. And, the direction flow
control valve 525 remains at neutral. The system 510 may remain in
the Sub-mode 3t until the operator inputs a command that no longer
lowers the boom 402 or rotationally decelerates the upper structure
412, the system load is changed from "on-target", and/or the
accumulator 534 sufficiently charges such that it can no longer
receive power. The Sub-mode 3t smoothly transitions the system 510
from the Sub-mode 3a to the Sub-mode 3b and thus changes (e.g.,
continuously changes) the displacement of the pump/motor 502. The
displacement of the pump/motor 502 may be set to match the
accumulator 534, and, when the accumulator 534 is fully charged,
the displacement of the pump/motor 502 is set to "e", where "e" is
some non-zero value sufficient to provide energy absorption from
the hydraulic cylinder 402c and/or the swing drive. As the pressure
Pacc of the accumulator 534 is at or near a relief pressure
Prelief, the value of "e" may be small and yet provide sufficient
braking torque. As the accumulator 534 is fully charged, hydraulic
fluid flow instead passes through the relief valve 535 and on to
the tank 518. The displacement of the pump/motor 502 and/or the
displacement of the pump/motor 500 may continuously be adjusted to
absorb the required torque and speed of the output/input shaft 536
and/or the hydraulic energy from the hydraulic cylinder 402c while
the accumulator 534 is charging and/or hydraulic fluid flow passes
through the relief valve 535.
[0077] Upon the accumulator 534 charging such that it no longer can
receive power, the system controller 542 automatically configures
the system 510 to a Sub-mode 3b. The Sub-mode 3b keeps the
pump/motor 502 configured at "e" displacement, keeps the pump/motor
500 configured as a motor, keeps the mode valve 567 set to fluidly
connect with the boom cylinder 402c, keeps the NFC valve 545 open,
keeps the clutch 540 engaged, and keeps the direction flow control
valve 525 positioned at neutral. The system 510 may remain in the
Sub-mode 3b until the operator inputs a command that no longer
lowers the boom 402 or rotationally decelerates the upper structure
412 or the system load changes from "on-target".
[0078] Conventional hydraulic linear and rotary actuators (e.g.,
hydraulic cylinders and hydraulic motors) used on work machines are
typically controlled using hydraulic valves in a throttling manner.
This process results in significant energy being wasted as heat is
generated from high pressure hydraulic fluid being metered. The
hydro-mechanical transformer 26c, when incorporated on the
hydraulic excavator 400 achieves boom and swing energy regeneration
and engine load leveling. According to the principles of the
present disclosure, a supervisory system control strategy for
recovering the inertial energy of the boom 402 and/or the swing of
the upper structure 412 is performed by the system controller 542
for the purpose of reducing the fuel consumption while maintaining
the hydraulic machine operation manner (i.e., the work machine
operating characteristics). The inertial energy of the boom 402
and/or the upper structure 412 is captured and recovered through
the hydro-mechanical transformer 26c and the accumulator 534.
[0079] In typical conventional excavators, the engine directly
powers the motion of all actuators (e.g., boom, arm, bucket
cylinders, and the swing motor). The engine power consumption
typically has a trend similar to the graph at FIG. 29. High power
output from the engine is required when the actuator serves high
pressure and/or high flow tasks (e.g., passive boom up). This high
energy used in the raising of the boom will eventually be
dissipated as heat when the boom falls in an over-running manner.
Similar energy waste happens when the swing motor is accelerated
and then braked hydraulically.
[0080] A similar engine power consumption trend for the
hydro-mechanical transformer system 510 is shown at FIG. 30.
According to the principles of the present disclosure, the
hydro-mechanical transformer 26c and the accumulator 534 provide
the energy storage and release capability to reduce the average
power supplied from the engine (i.e., the prime mover 514). When
the system 510 is used to level the engine load, the system 510
employs an "average power" as a decision point to determine whether
to supply energy with the transformer 26c or to store energy in the
accumulator 534. As the vehicle 400 is being operated, this
"average power" point adjusts as the power changes and the system
510 adapts to meet the operator's needs. For example, if the system
power requirement is higher than the average engine power, the
stored energy from the accumulator 534 will replace the pump 512
that is connected to the engine to serve (i.e., supply pressurized
hydraulic fluid to) the actuator (e.g., the hydraulic cylinder 402c
via the transformer 26c and/or the transformer 26c which actuates
the swing drive directly). If the system power requirement is lower
than the average engine power, the pump 512 connected to the engine
begins supplying energy to the transformer 26c and the energy is
stored in the accumulator 534. Load leveling decisions are also
impacted by accumulator charge and the operator commands.
[0081] In the energy regeneration modes, the system 510 ports fluid
from the cap end of the boom cylinder 402c, in the overrunning load
cases, to the transformer 26c and stores it in the accumulator 534.
The system 510 can directly drive the swing drive with the
accumulator pressure Pacc by supplying the transformer 26c with the
hydraulic fluid and activating the clutch 540 connected to the
lower structure-upper structure rotational drive. Energy can be
stored as the swing drive (i.e., the lower structure-upper
structure rotational drive) is braking by pumping hydraulic fluid
back into the accumulator 534 with the transformer 26c. In extreme
cases, when accumulator pressure Pacc is too low, the main engine
pump 512 can supply the actuators until the accumulator 534 has
enough pressure. The goal is to reduce the average engine power
consumption and thereby achieve fuel savings.
[0082] Manipulating the displacements of the two pump/motors 500
and/or 502 provides the infinite transformation ratios and the
energy flow direction (e.g., whether storing energy into the
accumulator 534, or release energy from the accumulator 534). The
mode valve 567 determines whether the transformer 26c is connected
with the main pump 512 output or directly connected to the boom cap
chamber of the boom cylinder 402c. The clutch 540 is inserted
between the transformer 26c and the swing service (i.e., the swing
drive). A proportional pump control valve or NFC valve 545 is
inserted to allow active control of the main pump 512 displacement
to achieve engine load leveling. The boom pilot valve can be set to
neutral to by-pass the command from the operator via the joystick.
In summary, six control efforts can be manipulated: the
displacements of the two pump/motors 500, 502, the mode valve 567,
the NFC valve 545, the clutch 540, and the boom valve 525. A brake
533 can further be manipulated.
[0083] Depending on the motions of the boom 402, the swing drive,
and the engine output power, various system states are defined,
including those mentioned above. Specific control actions are
determined for each of the modes. The control action serves two
goals. One goal is to guarantee the power requirement from the
services. The other goal is to optimize the energy recovering
efficiency. It is thus feasible to conduct power management via
dynamic programming and/or other trajectory optimization
techniques.
[0084] According to the principles of the present disclosure, the
system 510 is able to automatically transition between the various
sub-modes within a given mode. As mentioned above, certain of the
modes include the accumulator 534 that may be
operational--indicated by "a", may be transitioning--indicated by
"t", or may be non-operational in one direction--indicated by "b".
Sub-mode transition conditions are defined to achieve smooth
transients when transitioning among the sub-modes.
[0085] Among other operations, the system controller 542 seeks to
first satisfy control inputs from the operator to control the
excavator 400. The system controller 542 further seeks to utilize
energy stored in the accumulator 534 and seeks to return the
accumulator 534 to operational, indicated by sub-modes including an
"a" herein, upon the energy being spent from the accumulator 534.
The system controller 542 further seeks to capture energy and store
the energy in the accumulator 534. Sub-mode labels may include [a],
[b], and [t] that indicate that the accumulator 534 is operational,
non-operational, or transitioning, respectively.
[0086] According to the principles of the present disclosure,
additional modes may be defined for bypassing certain features
included in the above modes and/or sub-modes. Such additional modes
may be used, for example, when slight movements are required and/or
for movements that have insignificant energy capturing or reuse
potential.
[0087] According to the principles of the present disclosure, the
system 510 is able to transition between the various modes,
including the bypass modes. Mode transition conditions are defined
to achieve smooth transients when transitioning among the
modes.
[0088] Turning now to FIGS. 34-39, example flow charts illustrating
a method and/or methods of implementing control of a hybrid work
machine, according to the principles of the present disclosure, are
given. The modes illustrated at FIGS. 34-39 and described below may
overlap, may co-exist with, etc. the modes and the sub-modes
mentioned above, in certain embodiments.
[0089] FIG. 34 illustrates engine power leveling logic 600 (e.g.,
for the prime mover 514) according to the principles of the present
disclosure. The engine power leveling logic routine 600 calculates
engine power (e.g., of the prime mover 514) and evaluates the
engine power to determine if it is above a "PowerHi" value, between
the "PowerHi" value and a "PowerLow" value, or lower than the
"PowerLow" value. If the engine power is higher than "PowerHi",
then the engine power leveling logic 600 seeks to request
additional energy (i.e., power) from the accumulator (e.g., the
accumulator 34, the accumulator 234, the accumulator 534, etc.). If
the engine power is lower than "PowerLow", then the engine power
leveling logic 600 seeks to charge the accumulator (e.g., the
accumulator 534), if needed. By executing the engine power leveling
logic 600 in a control system (e.g., the controller 42, 542, etc.),
the peeks and/or the valleys in a typical work cycle may be
leveled, as mentioned above. In particular, the example engine
power leveling logic flow chart 600 begins at a starting point 602.
Upon starting, control advances to a calculate engine power routine
604 where engine power (e.g., actual engine power) is calculated.
Upon calculating the engine power, the control advances to a
decision point 606. At the decision point 606, the engine power
calculated at step 604 is tested to determine if the engine power
is higher than "PowerHi". If this result is "yes", the control
advances to routine 608 that sets a flag to require (i.e., request)
extra energy (i.e., power) from the accumulator (e.g., the
accumulator 534). Upon the completion and/or implementation of step
608, control advances to an accumulator usage routine 620. The
accumulator usage routine 620 is further illustrated at FIG. 35. If
decision point 606 results in "no", the control advances to
decision point 610. At the decision point 610, the engine power
calculated at step 604 is compared with the value "PowerLow". If
the result of step 610 is "yes", the control advances to routine
612. The routine 612 sets a flag indicating that engine power is
available to charge the accumulator (e.g., the accumulator 534).
Upon step 612 being completed and/or implemented, control advances
to the accumulator usage routine 620. If the decision point 610
results in "no", the control advances to step 604.
[0090] FIG. 35 illustrates the accumulator usage routine 620. The
accumulator usage routine 620 tests accumulator pressure Pacc in
the accumulator (e.g., the accumulator 534) to see if the
accumulator pressure Pacc is greater than a value "Phigh", is
between the value "Phigh" and a value "Plow", or is below the value
"Plow". By determining the state of the accumulator by measuring
and classifying the accumulator pressure Pacc, usage of the
accumulator can be properly determined and/or planned. In
particular, the accumulator usage logic 620 starts at a starting
point 622. Upon starting, the control advances to routine 624 where
the accumulator pressure Pacc is read. Upon reading the accumulator
pressure Pacc, the control advances to a decision point 626. At the
decision point 626, the accumulator pressure Pacc is tested against
the value "Phigh". If the result of the decision point 626 is
"yes", the control advances to routine 628 where a flag is set
indicating that the accumulator (e.g., the accumulator 534) is
available for discharge only. Upon the routine 628 being completed
and/or being implemented, the control advances to an end point 638.
Upon the decision point 626 resulting in "no", the control advances
to a decision point 630 where the accumulator pressure Pacc is
tested against the value "P low". If the result of the decision
point 630 is "yes", the control advances to a routine 632 where a
flag is set that the accumulator (e.g., the accumulator 534) is
available for charge only. Upon the routine 632 being completed
and/or being implemented, the control advances to the end point
638. Upon the decision point 630 resulting in "no", the control
advances to a routine 634. At the routine 634, a flag is set
indicating that the accumulator (e.g., the accumulator 534) is
available for charge and/or for discharge. The routine 634 is feed
by a routine 636 that imports the engine power leveling logic 600
and/or results of the engine power leveling logic 600 into the
routine 634. Upon the routine 634 being completed and/or being
implemented, the control advances to the endpoint 638.
[0091] Upon the endpoint 638 being reached, in certain example
embodiments, the accumulator usage routine 620 waits until a
trigger signal is given and thereby restarts the accumulator usage
routine 620 at the start point 622. In certain example embodiments,
the trigger point may be generated every 1 millisecond. In other
embodiments, other regular and/or irregular trigger point intervals
may be used. The accumulator usage routine 620 generally indicates
whether the accumulator (e.g., the accumulator 534) is full and
unable to acquire additional energy, is empty and unable to deliver
any energy, or is between full and empty and therefore is both able
to accept energy and/or deliver energy.
[0092] FIG. 36 illustrates a routine 650 that selects an operating
mode for a work machine (e.g., the hybrid excavator 400,
illustrated at FIGS. 24 and 25). The routine 650 starts at a
starting point 652. From the starting point 652, control advances
to a decision point 654. At the decision point 654, it is
determined whether a first actuator (e.g., a swing actuator and/or
a swing drive shaft 537) is stationary. If the decision point 654
results in "yes", the control advances to a routine 656 where a
clutch (e.g., the clutch 40, the clutch 240, the clutch 540, etc.)
is disengaged (e.g., disengaging the swing drive shaft 537 from the
output/input shaft 536) and a brake 533 is engaged. Upon the
routine 656 being complete, the control advances to a routine 700
(i.e., a boom only mode). The boom only mode 700 is illustrated at
FIG. 38 and may control the boom 402. Upon the decision point 654
resulting in "no", the control advances to a decision point 658
where it is determined if a second actuator (e.g., the boom
actuator 402c) is stationary. If the result of the decision point
658 is "yes", the control advances to a routine 670 (i.e., a swing
only mode). The swing only mode 670 is illustrated at FIG. 37 and
may control the swing (e.g., accelerate and decelerate pivotal
movement of the upper structure 412 about the pivot axis 408). If
the decision point 658 results in "no", a routine 740 (i.e., a "two
services" mode) is executed. The two services mode 740 is
illustrated at FIG. 39.
[0093] The routine 650 therefore determines whether the swing
(e.g., pivotal movement of the upper structure 412 about the pivot
axis 408) is stationary, the boom (e.g., the boom 402) is
stationary, or neither the swing nor the boom is stationary. By
determining whether the swing and/or the boom are stationary, a
boom only mode, a swing only mode, or a two services mode may be
correspondingly selected.
[0094] FIG. 37 illustrates the swing only routine 670. The swing
only routine 670 is simplified in that it has been predetermined
that the boom axis (i.e., the boom actuator 402c) is substantially
stationary. The swing only routine 670 determines whether a main
pump or main pumps (e.g., the pump 12, the pump 212, the pump 512,
etc.) are used, an accumulator or accumulators (e.g., the
accumulator 34, the accumulator 234, the accumulator 534, etc.) are
used, or the main pump (e.g., the pump 512) and the accumulator are
both used and shared to provide the swing actuator (e.g., the swing
drive shaft 537) of the excavator power. The swing only routine 670
further detects if the swing actuator is decelerating and thereby
provides opportunity to regeneratively charge the accumulator. The
swing only routine 670 is simplified in that it operates under a
predetermined condition of the boom actuator being substantially
stationary.
[0095] The swing only routine 670 starts at a starting point 672.
Upon starting at point 672, control advances to a decision point
674. At the decision point 674, a determination is made as to
whether the swing actuator is accelerating. As used in the example
herein, accelerating indicates that the rotational velocity of the
swing axis 408 is increasing in absolute value. Upon the decision
point 674 resulting in "yes", the control advances to a decision
point 676 where it is determined whether the accumulator (e.g., the
accumulator 534), is available for discharge. By discharging the
accumulator, energy from the accumulator may be used to move the
swing axis 408 of the excavator 400. Upon the decision point 676
being "yes", the control advances to a decision point 678. At the
decision point 678, it is determined if the accumulator (e.g., the
accumulator 534) has sufficient pressure to run the swing actuator
(e.g., the swing drive shaft 537). Upon the decision point 678
resulting in "yes", the control advances to a routine 680 where the
accumulator is used to actuate the swing actuator. Upon the routine
680 being completed and/or being implemented, the control advances
to an endpoint 690. Upon the decision point 674 resulting in "no",
the control advances to a decision point 682. At the decision point
682, it is determined whether the swing axis 408 of the excavator
400 is decelerating. As used in the example herein, decelerating
indicates that the rotational velocity of the swing axis 408 is
being reduced in absolute value. Upon the decision point 682
resulting in "yes", the control advances to a routine 684. At the
routine 684, the accumulator (e.g., the accumulator 534) is
charged, if appropriate. By charging the accumulator at step 684,
energy is captured from the swing and delivered and stored in the
accumulator. In particular, inertial energy of the excavator 400 is
converted to potential energy within the accumulator (e.g., the
accumulator 534). Upon the routine 684 being completed and/or being
implemented, the control advances to the endpoint 690. Upon the
decision point 682 indicating "no", the control advances to the
decision point 676. Upon the decision point 676 indicating "no",
the control advances to a routine 686 where a flag is set to use
the main pump (e.g., the pump 512) only to drive the swing axis of
the excavator. The main pumps or main pump is powered by the
engine/prime mover of the excavator. Upon the routine 686 being
complete and/or being implemented, the control advances to the
endpoint 690. Upon the decision point 678 being "no", the control
advances to a routine 688 where a flag is set that energy sharing
between the engine (e.g., the prime mover 514) and the accumulator
shall be used to actuate the swing actuator. As described above, a
transformer (e.g., the transformer 26c) may be used to balance the
pressure between the main pump driven by the engine and pressure
from the accumulator. The pressure may be balance by setting and/or
controlling one or both swash plates of the pump/motors 500, 502.
Upon the routine 688 being complete and/or being implemented, the
control advances to the endpoint 690. As mentioned above with
respect to FIG. 35, upon the endpoint 690 being reached, the swing
only routine 670 may wait until a signal restarts the routine 670
at the start point 672.
[0096] FIG. 38 illustrates the boom only routine 700. The boom only
routine 700 is simplified in that it has been predetermined that
the swing axis (i.e., the swing actuator) is substantially
stationary. The boom only routine 700 starts at a starting point
702. Upon starting at the start point 702, control advances to a
decision point 704. At the decision point 704 it is determined
whether the boom (e.g., the boom 402) is being actuated to go up
(e.g., moved against gravity). Upon the decision point 704
resulting in "yes", the control advances to a decision point 706
where it is determined if the boom up request results in a passive
boom up request. As used in the example embodiment herein,
"passive" indicates that energy is expended to effect the action.
If the result of the decision point 706 is "yes", the control
advances to a decision point 708. At the decision point 708, it is
determined if the accumulator (e.g., the accumulator 534) is
available for discharge. If the result of the decision point 708 is
"yes", the control advances to a decision point 710. At the
decision point 710, it is determined if the transformer flow and/or
pressure is sufficient to power the boom actuator (e.g., the boom
actuator 402c). Upon the decision point 710 resulting in "yes", the
control advances to a routine 712 where the accumulator (e.g., the
accumulator 534) is used alone to power the boom actuator. Upon the
routine 712 being completed and/or implemented, the control
advances to an endpoint 722. Upon the decision point 704 resulting
in "no", the control advances to a decision point 714. At the
decision point 714, it is determined whether a boom down motion is
overrunning or not. As used in the example embodiment herein,
overrunning indicates that energy recovery may be possible. In
particular, inertial and/or gravitational loads may be regenerated,
reused, and/or stored as useful energy. If the decision point 714
results in "yes", the control advances to a routine 716 where the
transformer is used to charge the accumulator, if appropriate. Upon
the routine 716 being completed and/or implemented, the control
advances to the endpoint 722. Upon the decision point 706 being
"no", the control advances to a routine 718. At the routine 718, a
flag is set indicating that the main pump should be used alone to
power the boom actuator. Upon the decision point 708 resulting in
"no", the control advances to the routine 718. Upon the decision
point 710 indicating "no", the control advances to a routine 720
where a flag is set that the boom actuator should be powered by
flow sharing between the main pump, driven by the engine, and
pressure and flow delivered by the accumulator via the transformer.
Upon the routine 720 being completed and/or implemented, the
control advances to the end point 722. Upon the decision point 714
being "no", the control advances to the routine 718. Upon the
routine 718 being completed and/or implemented, the control
advances to the endpoint 722.
[0097] FIG. 39 illustrates the two services mode 740. The two
services mode 740 is implemented when both the swing axis,
described in detail above, and the boom axis, described in detail
above, are moving simultaneously. The two services mode 740 starts
at a starting point 742. Upon starting at the starting point 742,
control advances to a decision point 744 where it is determined
whether the swing actuator (e.g., the swing drive shaft 537) is
accelerating. If the result of the decision point 744 is "yes", the
control advances to a decision point 746. At the decision point
746, it is determined whether the boom (e.g., the boom 402) is
being requested to go up. Upon the decision point 746 resulting in
"yes", the control advances to a decision point 748. At the
decision point 748, it is determined if the boom up movement is
passive. Upon the decision point 748 resulting in "yes", the
control advances to a decision point 750. At the decision point
750, it is determined whether the accumulator (e.g., the
accumulator 534) is available for discharge. If the result of the
decision point 750 is "yes", the control advances to a decision
point 752. At the decision point 752, it is determined whether the
accumulator pressure is sufficient for swing actuator movement.
Upon the decision point 752 resulting in "yes", the control
advances to a routine 754. At the routine 754, the transformer flow
capacity capability is determined. Evaluation of the accumulator
may be part of calculating the transformer's flow capability. Upon
the routine 754 being executed, the control advances to a decision
point 756. At the decision point 756, it is determined if the
transformer flow is sufficient for boom actuation. If the decision
point 756 results in "yes", the control advances to a routine 758
(see FIG. 31). At the routine 758, a flag is set to use the
transformer (e.g., the transformer 26c) for both boom and swing
actuation.
[0098] Upon the decision point 744 resulting in "no", the control
advances to a decision point 760. At the decision point 760, it is
determined whether the swing is decelerating. If the result of the
decision point 760 is "yes", the control advances to a decision
point 762 where it is determined if the boom is being commanded up.
Upon the decision point 762 resulting in "yes", the control
advances to a decision point 764 where it is determined whether the
boom up movement is passive. Upon the decision point 764 resulting
in "yes", the control advances to a routine 766. At the routine
766, the transformer flow capability is calculated. The calculation
of the transformer flow capability may include an evaluation of the
accumulator pressure. Upon routine 766 being executed, the control
advances to a decision point 768. At the decision point 768, it is
determined whether or not the transformer flow is sufficient to
drive the boom actuator. Upon the decision point 768 resulting in
"yes", the control advances to a routine 770 (see FIG. 31). At the
routine 770, a flag is set indicating that the transformer should
be used for both boom and swing movement.
[0099] Upon the decision point 746 resulting in "no", the control
is transferred to a decision point 772. At the decision point 772,
it is determined whether overrunning boom down motion is occurring.
Upon the decision point 772 indicating "yes", the control is
transferred to a decision point 774. At the decision point 774, it
is determined whether the boom is producing sufficient pressure
and/or flow to drive the swing actuator. Upon the decision point
774 resulting in "yes", the control is transferred to a decision
point 776. At the decision point 776, it is determined if the
accumulator is available for discharge. If the decision point 776
results in "yes", the control is transferred to a decision point
778. At the decision point 778, it is determined if the combined
accumulator and boom pressure are sufficient to drive the swing
actuator. If the result of decision point 778 is "yes", the control
is transferred to a routine 780 (see FIG. 42). At the routine 780,
a flag is set indicating that swing motion shall be produced by
energy sharing between boom down flow and accumulator flow. A flag
is also set indicating that the boom motion shall be produced by
flow sharing between the directional control valve (??) and the
transformer (e.g., the transformer 26c). Upon the routine 780 being
executed, the control is transferred to the endpoint 790.
[0100] Upon the decision point 750 resulting in "no", the control
is transferred to a routine 782 (see FIG. 33). At the routine 782,
a flag is set indicating that the engine (e.g., the main pump 512
driven by the engine 514) shall be used to drive both the swing
actuator (e.g., the transformer 26c driving the swing drive shaft
537) and the boom actuator (e.g., the boom actuator 402c). Upon the
routine 782 being executed, the control is transferred to the
endpoint 790. Upon the decision point 752 resulting in "no", the
control is transferred to a routine 784 (see FIG. 40). At the
routine 784, a flag is set indicating that the swing motion shall
be produced by flow sharing between the main pump, driven by the
engine, and the transformer, driven by the accumulator (e.g., the
accumulator 534). A flag is also set indicating that the boom
motion shall be powered by the main pump, driven by the engine.
Upon the routine 784 being executed, the control is transferred to
the endpoint 790. Upon the routine 756 resulting in "no", the
control is transferred to a routine 786 (see FIG. 32). The routine
786 sets a flag that indicates that the swing motion shall be
produced by the transformer alone. The routine 786 also sets a flag
that indicates that the boom motion shall be produced by flow
sharing between the directional control valve and the transformer.
Upon the routine 786 being executed, the control is advanced to the
endpoint 790. Upon the decision point 776 resulting in "no", the
control is transferred to the routine 782. Upon the routine 782
being executed, the control is transferred to the endpoint 790.
Upon the decision point 778 resulting in "no", the control is
transferred to the routine 782. Upon the routine 782 being
executed, control is transferred to the endpoint 790. Upon the
decision point 748 resulting in "no", the control is transferred to
a routine 670A.
[0101] At the routine 670A, the boom actuator is driven by the main
pump, powered by the engine alone. In addition, the routine 670A
transfers logic controlling the swing actuator to the logic of the
swing only mode 670, as illustrated at FIG. 37. Upon the decision
point 772 resulting in "no", the control is transferred to the
routine 670A. Upon the decision point 768 resulting in "no", the
control is transferred to the routine 786. Upon the routine 786
being executed, the control is transferred to the endpoint 790.
Upon the decision point 762 resulting in "no", the control is
transferred to the decision point 788. At decision point 788, it is
determined whether the boom down motion is overrunning. Upon the
decision point 788 resulting in "yes", the control is transferred
to the routine 766. Upon the routine 788 being "no", the control is
transferred to the routine 670A. Upon the decision point 764
resulting in "no", the control is transferred to the routine
670A.
[0102] Turning now to FIGS. 40-43, additional configurations of the
system 510 are illustrated. These additional configurations are
example configurations. Still other configurations of the system
510 are possible. In particular, FIG. 40 illustrates a
configuration in which engine energy from the engine 514 powers the
boom cylinder 402c, and in which engine energy from the engine 514
and accumulator energy from the accumulator 534 power the swing
drive shaft 537 (via the transformer 26c). FIG. 41 illustrates a
configuration in which engine energy from the engine 514 powers the
boom cylinder 402c, and in which engine energy from the engine 514
and swing deceleration energy charge the accumulator 534. FIG. 42
may illustrate a configuration in which the main pump 512 supplies
the boom cylinder 402c with flow, and the boom 402 is travelling
down in an over-running condition. Alternatively, flow may be
supplied to the boom cylinder 402c via the proportional valve 417.
FIG. 42 may further illustrate boom energy being transferred to the
accumulator and/or the swing via the transformer 26c. The energy
from the boom 402 can thus be used to charge the accumulator 534
and/or aid acceleration of the swing drive shaft 537. The energy
from the boom 402 can further be dissipated at the relief valve
535, if needed. FIG. 43 may illustrate a configuration in which
engine energy from the engine 514 powers the boom cylinder 402c,
and in which engine energy from the engine 514 charges the
accumulator 534 via the transformer 26c.
[0103] The present application is related to U.S. Provisional
Patent Application Ser. Nos. 61/523,099, entitled System and Method
for Recovering Energy and Leveling Hydraulic System Loads and filed
on Aug. 12, 2011; 61/523,110, entitled Method and Apparatus for
Recovering Inertial Energy and filed on Aug. 12, 2011; and
61/523,524 entitled Method and Apparatus for Recovering Inertial
Energy and filed on Aug. 15, 2011, and the disclosures of which are
hereby incorporated by reference in their entireties. The present
application is also related to U.S. patent application Ser. No.
13/571,517, entitled System and Method for Recovering Energy and
Leveling Hydraulic System Loads and filed on Aug. 10, 2012, and
Ser. No. 13/572,115, entitled Method and Apparatus for Recovering
Inertial Energy and filed on Aug. 10, 2012, and the disclosures of
which are hereby incorporated by reference in their entireties.
[0104] Various modifications and alterations of this disclosure
will become apparent to those skilled in the art without departing
from the scope and spirit of this disclosure, and it should be
understood that the scope of this disclosure is not to be unduly
limited to the illustrative embodiments set forth herein.
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